When artists and scientists collaborate, it’s usually because an artist wants to make a piece of art inspired by some scientific concept. But in Chicago, an artist is helping a biologist uncover something about the climate. Shane DuBay is an evolutionary biologist and Carl Fuldner is an art historian, both getting their PhDs at the University of Chicago. The two have been photographing bird specimens at The Field Museum from the last century and a half — and they noticed something strange: The feathers on the birds from a long time ago looked dirtier than newer specimens. DuBay and Fuldner used software to analyze their photographs of the birds and figured out that dinginess of their plumage correlates to the changing amount of air pollution. Which suggests that during the age of impressionist painting, all those magnificent landscapes, the new coal-powered factories were making the air dirtier than ever before — or since.